1. Field of the Invention
The present invention relates to the field of passive solar energy heating units which may be installed in building walls in the manner of windows.
2. Description of the Related Art
Passive solar heating units of the subject type are known in the art. For example, U.S. Pat. No. 4,532,917 to Taff et al. shows a modular passive solar energy heating unit for heating an enclosed space. The unit employs phase change heat storage material, which is optically transparent to visible light when in a high-stored-energy liquid state, enabling a viewer to see through clearly, and which is translucent milky white when in a low-stored-energy solid state for providing pleasant illumination to the enclosed space when first illuminated by sunlight in the morning.
An undesirable characteristic of this and other such modular passive solar energy heating units of the prior art is their tendency to radiate too much of the heat stored during the daylight hours back outside the building at night. As a consequence, less of the stored heat remains available to heat the building at night. In addition, the heat that does remain to be transmitted into the building does so too quickly, with the result that its benefit is felt for only a relatively short time.
International Publication No. WO 2008/054497 A2, the teachings of which are incorporated herein by reference, shows a solar heating block designed for use in assembling solar heating panels in the walls of buildings. The solar heating block has a first compartment and a second compartment within its interior volume. The first compartment contains a translucent insulating material, such as an aerogel. The second compartment, which is inward of the solar heating block from the first compartment when the solar heating block is part of a solar heating panel in a building, contains a heat-absorbing material. The translucent insulating material allows light to be transmitted through the solar heating block, but reduces heat loss to the exterior of the building from the heat-absorbing material. Insulating fabric tiles may be installed on the surfaces of the solar heating blocks inside the building to moderate the rate at which the solar heating blocks release stored heat into the room.
The solar heating blocks shown in International Publication No. WO 2008/054497 A2 stack upon and interlock with one another to form a solar heating panel essentially lacking a separate framework. A disadvantage of this approach has been that it has been necessary to disassemble, at least to some degree, the solar heating panel to repair or to replace one of its solar heating blocks. Another disadvantage has been that air bubbles, which form in the heat-absorbing material, typically a mixture primarily including water, rise to the top of the second compartment of the solar heating block and combine to form a larger bubble that remains in view from the inside of the building. Attempts to hide or remove these bubbles have heretofore not been entirely successful.
The present invention provides a solution to these and other problems of the prior art.